1. Field of the Invention
The present invention relates to engine manufacturing, and more specifically, is concerned with a method of feeding carburetter engines and a carburetter for carrying out the same.
The invention may be used everywhere where internal combustion engines with carburation having an external ignition source are employed, in particular, on transport vehicles such as, for instance, motor cars.
2. Prior Art
Saving of hydrocarbon fuel and environment protection to prevent exhaust product pollution of the environment are the most urgent problem throughout the world. The main consumers of the hydrocarbon fuel are motor-car engines which are at the same time the main sources of atmospheric pollution. Therefore, decreasing the specific consumption of fuel in internal combustion engines, developing and using new types of fuel and reducing the toxicity of exhaust gases are of paramount importance in solving the above problems.
Transport vehicles powered with carburetter engines are most extensively used at present, since these engines are characterized by a high specific power and good dynamic characteristics, and in addition they are not expensive.
Main disadvantages these engines have are a high fuel specific consumption (210-270 g-equ hp per hour) and a high content of toxic substances in the exhaust products. This is caused by that at a low and mean loads on a shaft of the engine the latter has to operate on a combustible mixture, in particular on a petrol-air mixture, having an excess-air coefficient (hereinafter referred to as ".alpha.") lower than 1. For instance, in the case of no-load (idle) running (at a minimum load on a shaft) the coefficient .alpha. must be equal to 0.6 and at a maximum load it must be in the range from 0.85 to 0.95. In the latter case the combustion velocity of the petrol-air mixture is maximum. In this case, however, a portion of the fuel does not burn and is carried away by the exhaust gases in the form of a carbon oxide or non-oxidized hydrocarbons.
With the increase of the coefficient .alpha. the combustion velocity decreases, which results in a lower engine power output. In this case if .alpha.&gt;1.3 said petrol-air mixture generally cannot be ignited in a combustion chamber, since it is a well known fact that said mixture may be ignited only provided that 0.6&lt;.alpha.&lt;1.3. This leads to that regulating the operating conditions of the engine can be effected only by varying the quantity of the combustible mixture through its throttling at the entrance to the engine by means of a choke valve. Such throttling, however, at a low and a mean loads, in which case the coefficient of filling of the cylinders is from 0.1 for a no-load running to 0.4-0.5 at mean loads, leads to the increase of the fuel specific consumption.
The problem of fuel saving and of decreasing the toxicity of the exhaust gases may be partially solved by replacing the carburetter engines with diesel engines, which is done in fact in most countries. A diesel engine features a lower fuel specific consumption (155-190 g-equ hp per hour) but because of its complex fuel-feed equipment and the use of expensive wear resistant materials it is 1.5-2 times more expensive than a comparable carburetter engine Furthermore, the specific power of a diesel engine is generally 0.2-0.4 hp per kg, which is 1.5-3 times lower than that of carburetter engines. It is also to be noted that diesel engines have lower dynamic characteristics and relatively a higher content of nitrogen oxides and soot in the exhaust gases.
Therefore, a more simple way of reducing the fuel specific consumption and the exhaust gases toxicity is to improve the carburetter engine, and in particular to develop a new method of feeding carburetter engines and improve the carburetters.
An economical operation of engine may be considerably improved with a simultaneous decrease in the toxicity of the exhaust gases by using hydrogen as an additive to hydrocarbon fuel (petrol), that is by forming a combustible mixture from three components namely, petrol, hydrogen and air.
In the description of the invention relating to a carburetter which has been proposed by us earlier (cf. USSR Author's Certificate No. 670,739, Int.Cl.sup.2 F02M25/10) is also disclosed a method of feeding carburetter engines, wherein the combustible mixture is formed from a petrol-air mixture and a hydrogen-air mixture and then fed to the engine with the proportions of the components in said mixture being regulated depending on the load on the engine shaft. This control is effected by varying the quantity of the petrol-air mixture and the quantity of and component proportions in the hydrogen-air mixture. However, the quantities of the components contained in the combustible mixture being formed ae not specified; there are given only air-excess coefficients .alpha.. Thus, for idle running .alpha.=4.5 and at a full load .alpha.=1.
A carburetter (see the above-mentioned Author's Certificate) to practice this method of feeding an engine comprises a mixing tube connected to the intake manifold of the engine, a first and a second choke tubes for forming a petrol-air mixture and a hydrogen-air mixture, both communicating with said mixing tube, as well as a petrol supply and a hydrogen supply units. The first choke chamber has a choke valve to control the quantity of the petrol-air mixture in the resultant combustible mixture. The petrol supply unit comprises a float chamber and a main dosage chamber communicating said float chamber with the first choke tube. The hydrogen supply unit comprises an injector fitted into the second choke tube and a hydrogen-feed regulator. The said regulator has a body provided with an inlet pipe to intake hydrogen and an outlet pipe to feed hydrogen to the injector, for which purpose said inlet pipe is connected to said injector. This regulator also includes a working member disposed in said body and intended to regulate the quantity of the hydrogen fed to said injector.
It has been established that a higher efficiency of the above method of feeding a three-component combustible mixture to an internal combustion engine as compared to the prior art method of feeding a two-component mixture (petrol-air-mixture) to an engine of a similar type, is explained by that the combustion velocity of a combustible mixture composed from petrol, hydrogen and air, in which mixture the amount of hydrogen is from 1 to 15% of the total amount of the hydrogen and petrol and the coefficient .alpha. is equal to from 1 to 1.15, corresponds to the burning velocity of a petrol-air mixture (without hydrogen) whose coefficient .alpha. is equal to from 0.85 to 0.95, that is to the maximum combustion velocity in an engine operating on a two-component combustible mixture. Also, in this case the engine power output obtained will be equal to that obtained in the case of feeding to the engine a two-component combustible mixture with .alpha.&gt;1, which in the end leads to a higher efficiency of the engine.
Further leaning of the combustible mixture above .alpha.=1.3, the stability of its burning due to the presence of the hydrogen is not disturbed even at .alpha.32 7. In this case when .alpha. is increased from 1 to 7 the hydrogen content in the combustible mixture increases and at a maximum value of .alpha. reaches 100%.
In this method, therefore, at low an mean loads (beginning from idle running to loads constituting 0.4-0.6 of the full load) the engine is fed with a lean mixture. Thus in the case of idle running the coefficient .alpha. is 4.5-7, and at mean loads said coefficient is 1.8-2.2. This to a certain extent improves the efficiency of the engine and decreases the exhaust gases toxicity.
It should be noted, however, that in practising the above method with the use of said carburetter there are experienced a number of difficulties. First, even with the use of such a relatively efficient method the efficiency of the engine at low and mean loads remains relatively low, which perhaps may be explained by a considerable loss of heat through exhaust gases.
Furthermore, at .alpha.=4.5-7 the engine can operate only with large (50.degree.-70.degree. ) angles of advance, which requires more complex ignition system. In addition, at a minimum no-load running speeds there occurs a relatively high consumption of the hydrogen (for the engines with the displacement volume of 2500 cu cm it constitutes not less than 0.2-0.3 kg per hr). It should also be noted that any attempt to increase the efficiency of the engine employing the prior art method inevitably leads to the increase in the exhaust gases toxicity.